KA3 The biology of controlling fertility

Question 1

When are males fertile?

Answer 1

Males are continuously fertile because they continually produce sperm in their testes

Question 2

When are females fertile?

Answer 2

Women are only fertile for a few days during each menstrual cycle. Their fertility is described as cyclical

Question 3

How is a women’s fertile period indicated?

Answer 3

1- The cervical mucus secreted into the vagina is thin and watery
2- The woman’s body temperature rises by around 0.5 degrees

Question 4

How can ovulation be stimulated if there is a failure of the pituitary gland to secrete adequate FSH or LH?

Answer 4

• Drugs that prevent the negative feedback effect of oestrogen on FHS secretion (keeping FSH high to be able to develop more ova)
• Drugs that mimic the action of FSH and LH. These drugs can be so effective they cause “super ovulation” which can lead to multiple births or be used to collect ova (eggs) for IVF

Question 5

What is Artificial Insemination?

Answer 5

Several samples of semen are collected over a period of time.
It is the introduction of semen into the female reproductive tract.
It is particularly useful when the male has a low sperm count.
If a partner is sterile a donor may be used to provide semen.

Question 6

What is Intracytoplasmic Sperm Injection (ICSI)?

Answer 6

If mature sperm are defective or very low in number ICSI may be used. The head of the sperm is drawn into a needle and injected directly into the egg to achieve fertilisation.

Question 7

How does In-vitro Fertilisation (IVF) work?

Answer 7

• There is the surgical removal of eggs after hormone stimulation.
• Eggs are mixed with sperm in a culture dish.
• The fertilised eggs are incubated until they have formed at least eight cells and are then transferred to the uterus for implantation

Question 8

How is IVF used in conjunction with pre- implantation genetic diagnosis (PGD)?

Answer 8

PGD is a form of genetic testing, exercised on embryo cells produced during IVF cycles to be able to know the genetic profiles of the embryo. It can be used to identify single gene disorders and chromosomal abnormalities

Question 9

What are the physical methods used to prevent pregnancy?

Answer 9

• Barrier method which physically blocks the ability of the sperm to reach the ovum eg condom or cervical cap
• Intra Uterine device is a plastic T shaped structure with copper wound around its outside, it prevents the implantation of an embryo.

Question 10

What are sterilisation procedures used to prevent pregnancy?

Answer 10

• Vasectomy involves cutting and tying the two sperm ducts which prevents sperm being released.
• Tubal ligation involves cutting and tying the two oviducts which prevents eggs meeting sperm

Question 11

What are oral contraceptive pills?

Answer 11

They usually contain synthetic oestrogen combined with synthetic progesterone that mimics the body’s negative feedback preventing the release of FSH and LH from the pituitary gland.

Question 12

What are emergency contraceptive pills?

Answer 12

They prevent or delay ovulation and prevent the implantation of a blastocyst. The “morning after pill” can be taken up to 72 hours or 120 hours after unprotected sex depending on which type of pill is used. They contain higher doses of hormones than the standard oral contraceptive pill.

Question 13

What are progesterone- only pills?

Answer 13

The “mini pill” does not contain synthetic oestrogen. Mini pills thicken the cervical mucus reducing the viability of sperm.